1. Field of the Invention
The present invention relates to an image recording apparatus that comprises a line head including a plurality of jetting nozzles and jets ink onto a recording medium from the plurality of jetting nozzles of the line head, and more particularly, to an image recording apparatus where one line head is formed by arranging a plurality of short recording heads, and to a controlling method thereof.
2. Description of the Related Art
Conventionally, for example, a full-line image recording apparatus of an inkjet type is known as an image recording apparatus that executes a recording process for a recoding medium such as paper or the like on the basis of recording data.
In the full-line image recording apparatus, nozzle rows (recording heads) each of which is formed along a length equal to or more than a width of a recording medium in a direction (main scanning direction) orthogonal to a conveyance direction (sub-scanning direction) of conveying the recording medium and is composed of a plurality of nozzles jetting ink droplets are provided for respective ink colors. The nozzle rows for the respective ink colors are separated at predetermined intervals in the sub-scanning direction and are provided so that the nozzles face the recording medium.
Such an image recording apparatus can execute a recording process onto the entire surface of a recording medium only by relatively moving a recording medium and a line head including nozzle rows in a direction nearly orthogonal to the direction of arranging the nozzles. Accordingly, the full-line image recording apparatus can quickly execute the recording process with simple operations without performing operations such as moving a carriage, intermittently conveying a recording medium, and the like.
In contrast, a line head used in a full-line type has problems of high cost, poor yield, low reliability and the like compared with a short recording head.
Image recording apparatuses that solve these problems include an apparatus having a line head where jetting nozzles are formed by arranging a plurality of short nozzle rows arranged in one direction of arranging nozzles. Such a line head has not only advantages, such as low cost, good yield, high reliability and the like, of a short nozzle row but advantages of a line head.
These image recording apparatuses have a problem in that streak-shaped density unevenness, a white spot and the like are prone to occur because of including the above described line head composed of short nozzle rows, and diverse techniques for decreasing streak-shaped density unevenness, a white spot and the like have been proposed.
For example, Patent Document 1 (Japanese Laid-open Patent Publication No. 2001-328245) discloses an image recording head in which dot diameters are formed to become sequentially smaller by sequentially decreasing nozzle diameters toward an edge, and which reduces density unevenness even if an obliquely proceeding recording medium is printed.
Additionally, for example, Patent Document 2 (Japanese Laid-open Patent Publication No. 2002-144542) discloses an image recording method for arranging adjacent short nozzle rows, part of which is made to overlap. The image recording method according to Patent Document 2 eliminates the need for precisely aligning the short nozzle rows in order to prevent a pitch of recording elements at a joint from becoming unsuitable, and this method can record an image of high quality free from color/density unevenness and the like.